Infant and pediatric cholestatic liver diseases are rare yet devastating conditions. Biliary Atresia (BA) and idiopathic neonatal hepatitis, studied under the Biliary Atresia Research Consortium, along with Alagille syndrome (AGS), alpha-1-antitrypsin deficiency, progressive intrahepatic cholestasis, bile acid synthesis defects, mitochondrial hepatopathies, and cystic fibrosis liver disease, studied under the Cholestatic Liver Consortium collectively represent the vast majority of causes of cholestatic liver diseases in children. The Childhood Liver Disease Research and Education Network (ChiLDREN) will serve as the merged entity by which the research efforts from both previously NIH-funded networks will continue to coordinate investigative efforts focused on these significant pediatric liver diseases. Currently, patients from the large and ethnically diverse population of Southern California served by Childrens Hospital Los Angeles (CHLA) are not recruited into either network. In order to establish a new ChiLDREN CC at CHLA, we propose the following specific aims: 1) Operationalize the CHLA ChiLDREN CC organizational infrastructure, screen and enroll eligible subjects in ChiLDREN for collection of clinical data and specimens for testing, processing, storage, and shipping to the consortium repositories;participate in the biliary atresia steroid safety and efficacy clinical trial.2) Establish mechanisms for outreach into the region including the counties of Los Angeles, Orange, Ventura, San Luis Obispo, Kern, Riverside, and San Bernardino including a toll-free referral line and distribute IRB-approved documents to network of potential healthcare provider referral sources for all infant cholestatic liver disease cases;and develop educational tools to increase awareness of pediatric liver diseases including education rounds at outlying hospitals as well as mass mailings of educational flyers.3) Collaborate with the other CC investigators and participate in the organization and operation of ChiLDREN through ongoing conference calls and meetings and provision of scientific input and proposals for ancillary studies;ancillary project proposal: Characterize alterations in signaling pathways involved in hepatic progenitor cell fate contribute to the pathogenesis of BA and AGS. Relevance: Infant and pediatric cholestatic liver diseases are rare. Alone, individual hospitals cannot accumulate sufficient experience to make meaningful scientific contributions which are the basis for the management algorithms of these diseases. ChiLDREN will facilitate the accrual of larger cohorts of patients with these rare diseases to advance knowledge and treatment of these devastating diseases.